Base-catalysed condensation of
1,3-bis(5-tert-butyl-2-hydroxyphenyl)propane 5 with
formaldehyde in xylene has been carried out to form the novel
propane-bridged calixarene-type macrocyclic compound,
tetrahydroxy[3.1.3.1]metacyclophane 6. The optimum yield (90%) of 6 is
obtained with NaOH as the base, the use of other alkali-metal hydroxides
giving lower yields. AlCl
3
–MeNO
2
-catalysed
trans-tert-butylation of 6 in benzene affords 7 in 80% yield.
Intramolecular hydrogen bonding has been observed in the tetraols 6 and
7 as comparable to calix[4]arene.
Methylation of 7 with MeI affords the tetramethoxy derivative 11a.
The stability of multi-membered carbon skeletons permits the
interconversion of functional groups at the lower and upper rims without
special regard to ring-opening side-reactions on the upper rim. For
example, the introduction of Br, formyl and acetyl substituents has been
achieved by electrophilic aromatic substitution of the tetramethoxy
derivative 11a. The
1
H NMR spectral behaviour of these
macrocyclic metacyclophanes is also discussed.